请看这段话

That is correct. Trace levels of lead can be found in balsamic and red wine vinegars, which are likely absorbed by the grapes from the soil in which they are grown or the wooden barrels in which they are sometimes matured. You probably wouldn’t know about it if it hadn’t been for a lawsuit filed by a California environmental group several years ago. The warning labels on balsamic vinegar are now the consequence of that case.